The present invention relates generally to analog phase shifters, and more specifically to high power ferrite microwave phase shifters.
Ferrite phase shifters are known that employ an applied magnetic field to vary the permeability of ferrite, thereby controlling the velocity and thus the phase shift of signals propagating through the phase shifter device. A conventional ferrite phase shifter comprises a rectangular waveguide structure, a ferrite slab loading and at least partially filling the waveguide, and a coil of wire wrapped around the waveguide. The wire coil is configured to carry a variable control current for generating a magnetic field, which is transversely applied to the ferrite slab to shift the phase of signals propagating in the rectangular waveguide structure.
One shortcoming of the conventional ferrite phase shifter is that the phase shifter device can become rather large and bulky when configured to carry lower frequency microwave signals. Such large bulky ferrite microwave phase shifters can also be costly to manufacture and thus not amenable to high volume production processes.
It would therefore be desirable to have a more compact ferrite phase shifter for handling microwave signals. Such a ferrite microwave phase shifter would be low cost and suitable for manufacturing in high volume production processes. It would also be desirable to have a compact ferrite microwave phase shifter that can be used in high power applications.
In accordance with the present invention, a high power ferrite microwave phase shifter is provided that is both compact and low cost. Benefits of the presently disclosed invention are achieved by providing a waveguide structure that not only reduces the size of the phase shifter device, but also enhances the effectiveness of applied Radio Frequency (RF) magnetic fields.
In one embodiment, the high power ferrite microwave phase shifter comprises a waveguide structure including a first substantially cylindrical element and a second substantially cylindrical element, in which the radius of the second cylinder is less than the radius of the first cylinder. The second cylindrical element is disposed within the first cylindrical element such that the first and second cylinders have a common axis of symmetry. The waveguide structure further includes a first septum formed as a disk and disposed within the second cylinder. The disk has a pie-shaped aperture formed therethrough that extends through the circumference of the disk and tapers to the disk center. The disk is centrally disposed within the second cylindrical element such that the first cylinder, the second cylinder, and the disk share the same axis of symmetry. The second cylinder has an opening formed therethrough that extends the full length of the second cylinder. The inner wall of the second cylinder is coupled to the circumferential edge of the disk such that the opening in the second cylinder is aligned with the pie-shaped aperture in the disk. The second cylinder is thus coupled to the disk without obstructing the pie-shaped aperture. The waveguide structure further includes a second planar septum that extends from the inner wall of the first cylinder to the disk center while bisecting the pie-shaped disk aperture. The second septum is coupled to the inner wall of the first cylinder and the disk at the disk center such that the second septum is approximately perpendicular to the plane of the disk.
In a preferred embodiment, the ferrite microwave phase shifter is loaded and totally filled with ferrite. The ferrite microwave phase shifter includes a coil of wire wrapped around the circumference of the first cylinder and configured to carry a variable control current for generating an RF magnetic field, which is transversely applied to the ferrite for controllably shifting the phase of signals propagating in the compact waveguide structure.
Other features, functions, and aspects of the invention will be evident from the Detailed Description of the Invention that follows.